product_invoiced_line/views/product_template.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="product_template_only_form_view" model="ir.ui.view">
            <field name="model">product.template</field>
            <field name="inherit_id" ref="product.product_template_only_form_view"/>
            <field name="groups_id" eval="[(4, ref('account.group_account_invoice'))]"/>
            <field name="arch" type="xml">
                <xpath expr="//div[@name='buttons']" position="inside">
                   <button class="oe_inline oe_stat_button" name="action_view_pt_supplier_invoice_lines" type="object"
                       icon="fa-shopping-cart">
                       <field string="Sup. Inv. Lines" name="sup_inv_lines_count" widget="statinfo"/>
                   </button>
                   <button class="oe_inline oe_stat_button" name="action_view_pt_customer_invoice_lines" type="object"
                       icon="fa-strikethrough">
                       <field string="Cus. Inv. Lines" name="cus_inv_lines_count" widget="statinfo"/>
                   </button>
                </xpath>
            </field>
        </record>
    </data>
</openerp>